ArticlePhysics & AstronomyIn situ carrier tuning in high temperature superconductor Bi2Sr2CaCu2O8+δ by potassium deposition

We report a successful tuning of the hole doping level over a wide range in high temperature superconductor Bi2Sr2CaCu2O8+δ (Bi2212) through successive in situ potassium (K) deposition. By taking high resolution angle-resolved photoemission measurements on the Fermi surface and band structure of an overdoped Bi2212 (Tc = 76 K) at different stages of K deposition, we found that the area of the hole-like Fermi surface around the Brillouin zone corner (π,π) shrinks with increasing K deposition. This indicates a continuous hole concentration change from initial ~0.26 to eventual 0.09 after extensive K deposition, a net doping level change of 0.17 that makes it possible to bring Bi2212 from being originally overdoped, to optimally-doped, and eventually becoming heavily underdoped. The electronic behaviors with K deposition are consistent with those of Bi2212 samples with different hole doping levels. These results demonstrate that K deposition is an effective way of in situ controlling the hole concentration in Bi2212. This work opens a good way of studying the doping evolution of electronic structure and establishing the electronic phase diagram in Bi2212 that can be extended to other cuprate superconductors.